Macrocytosis Without Megaloblastic Changes

Causes of non-megaloblastic macrocytosis

• Alcohol (may not be associated with anaemia)

• Liver disease (may not be associated with anaemia)

• Hypothyroidism (may not be associated with anaemia)

• Marrow failure (associated with anaemia)
• Myelodysplasia, myeloma, anaplastic anaemia

Spurious (false) macrocytosis

• The volume of the mature red cell is normal, but the MCV is measured as high

• Important examples include:
• Reticulocytosis in response to acute blood loss or red cell breakdown - reticulocytes are bigger than mature red cells
• Cold-agglutinins - cause RBCs to clump at temperatures lower than core body temperature, making them appear as one giant cell
• Ensure sample is warmed to 37℃